Engine Stroking My 302 To A 347, General Questions.

I am not the most mechanically inclined, but I am no where near afraid of getting my hands dirty. I love learning more about engines in generally, I am studying engineering for goodness sakes. I am a powerhog and would love to get more out of my stock 302, I hear stroking that bad boy out is a good way to get some more ponies. However, since I am new to all of this, I have some questions.

1. What are the negative effects of stroking out an engine, long term or short term?
2. Which would give me more power, stroking or boring out the engine? Can you do both? Should you?
3. I will most likely have a shop do the conversion, what should I pay for a job like this, including pulling and re-installing the engine?
4. I will most likely buy a kit, what is a really good kit?
5. What is some information I should know when doing this?

A 347 is bored .030 over, from a 4.00" bore to 4.030", and uses a stroker crank, goes from the standard 3.0" stroke to a 3.40". So yes you do both bore and stroke.

A lot of people think 347s have oil control problems but that is not true.

I would look into a SCAT kit.

Since you said stock 302 I'm assuming you have stock heads and intake? If so they will REALLY choke a 347. 302 parts make 302 power. You might gain some low end power but you won't have any top end at all. A nice set of Trickflows or AFR heads, a good intake and cam and you can make 400+ hp at the wheels NA on a 347. But don't forget you also have to have supporting mods to handle and supply the new power. Upgraded fuel system, suspension and neither the stock T5 or AOD transmissions will live too long behind that much power. Just got real expensive real fast lol

Yes I have stock EFI 302. My goals for the car is to get as close to 500 RWHP as possible all motor, then pop in a nice pretty turbo charger. So the kit does not come with heads or a cam? I am currently working on the suspension. I have new rear upper and lower control arms. I have some shocks and struts that are on back order on the way. I am going have someone weld in some equal length sub-frame connectors, then I am going to get a struct tower brace, and I think that is all I am going to do to the suspension. Then I will move on to the motor and will add a electric fan, then I will try to get in all those expensive motor upgrades.

Yes I have stock EFI 302. My goals for the car is to get as close to 500 RWHP as possible all motor, then pop in a nice pretty turbo charger. So the kit does not come with heads or a cam? I am currently working on the suspension. I have new rear upper and lower control arms. I have some shocks and struts that are on back order on the way. I am going have someone weld in some equal length sub-frame connectors, then I am going to get a struct tower brace, and I think that is all I am going to do to the suspension. Then I will move on to the motor and will add a electric fan, then I will try to get in all those expensive motor upgrades.

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The stock 302 block won't handle 500whp long. Once you get in the neighborhood of 500hp at the crank you are in the danger zone. The danger being splitting the block in half. IMO if you want 500whp, build a 351 based stroker. 90% of the parts between 302s and 351s swap back and forth and the cost to build a 351 is hardly any more expensive than building a 302 based stroker. And the stock 351w block will handle quite a bit more power.

Check out fordstrokers.com. They have a great reputation and have really good prices and will work with you on a payment plan.

Go to coast high performance online and get their scat kit lets just say this i had pulled and installed my motor disassembled it for the machinist and he bought parts and gave me a 3angle valve job and charged my 7 grand for the job which included an engine dyno to see how everything was working out

So you are saying in order to safely achieve the power I want, I need to switch over to a 351? Did ford make a 351 EFI?

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Yes. You want a '94 and up block because they are the only ones set up for a roller cam, although you can convert an older block. 500rwhp is doable with a 331 or 347 stroker and spray or boost but with a stock block it will just be a ticking time bomb. You can buy an aftermarket 302 block such as a dart or boss blocks but they are pretty expensive. For that much wheel hp you would need close to 600 at the crank. That is gonna be very hard to do without nitrous or boost and still have good street manners

SN Certified TechnicianMod Dude

Yes. You want a '94 and up block because they are the only ones set up for a roller cam, although you can convert an older block. 500rwhp is doable with a 331 or 347 stroker and spray or boost but with a stock block it will just be a ticking time bomb. You can buy an aftermarket 302 block such as a dart or boss blocks but they are pretty expensive. For that much wheel hp you would need close to 600 at the crank. That is gonna be very hard to do without nitrous or boost and still have good street manners

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While I agree completly about the block selection, I disagree about street manners. I have personally driven plenty of high hp legitimate street cars. My buddies 69 Camaro for starters made 1,000 rwhp has a 540 cu in big block with twin ysi Vortechs, power steering a/c and drives like my grand moms buick. Another friend has a 73 Mach 1 with a 408 stroker and Ysi Vortech 850 rwhp p/s a/c and awesome street manners. This car goes everywhere and has been on numerous TS cruises over the years with no problems. It's all in the tune or the tuners ability in my opinion. Heck we even took my Ttop car for a few rides around town and never had a hiccup.

While I agree completly about the block selection, I disagree about street manners. I have personally driven plenty of high hp legitimate street cars. My buddies 69 Camaro for starters made 1,000 rwhp has a 540 cu in big block with twin ysi Vortechs, power steering a/c and drives like my grand moms buick. Another friend has a 73 Mach 1 with a 408 stroker and Ysi Vortech 850 rwhp p/s a/c and awesome street manners. This car goes everywhere and has been on numerous TS cruises over the years with no problems. It's all in the tune or the tuners ability in my opinion. Heck we even took my Ttop car for a few rides around town and never had a hiccup.

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I'm not doubting high hp street cars at all, especially with more cubes. I just think that making 500rwhp NA out of a 347 might be difficult to do without losing some street manners.

I personally know of a 2011 5.0 with a Paxton setup making 850hp and the guy drives it about 80 miles per day and still.gets close to 20mpg. I definitely agree that big power doesn't necessarily mean poor street manners

theres no way your ever going to get 500rwhp out of a 347 and expect it to have any kind of setup that will be boost friendly

short of e85 with a set of CHI heads and a wicked cam

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agreed. my n/a 347 made 550hp but it had a 650 solid lifter cam, 11:1 pistons, etc. ,and was no where near a DD. It was not a stock 302 block either. Once you start getting over 400hp on a stock block, you are playing with fire. Ive seen guys- including myself - have gone over 400hp with a production block. But I've also seen guys split a production block down the middle with a little over 300hp.

If you are serious in making over 400hp then I would say get a boss or dart block and do it right the first time. Or you can build a 408 and easily get into the 400hp+ range with a good shortblock, cam and a set of heads.

x2 a stroked 408 with a GOOD set of CNC heads can have you where you want to be

keep in mind a turbo setup is going to be in some aspects opposite as compared to making power N/A, for example, a smaller cam and bigger heads and intake usually benefit a boosted engine, where as N/A you want to properly size your setup to optimize velocity

The best advice i can give is to read over the pre tuning information, a ton of info and tips that you wont find anywhere else

Founding Member

a buddy and i built a nasty 347 that ran low 10s @ 132 on motor. it only made 388rwhp. high compression, a big solid roller, a decent sized set of heads. 7500+ shift point. it was an early 302 block with a scat 9000 crank. it has been together for 4 years and made enough $ to pay for itself, but after a season we pulled the main caps off and it had severe cap chatter. its a ticking time bomb.

the stock shortblock in my 93 mustang made 490rwhp with a little set of 160cc gt40 irons, a ported gt40 lower, a downs box upper and a turbo technology street kit with a 60mm turbo at 12lbs of boost over 15 years ago. it ran high 10s/low 11s at 126mph. i drove that car like that for 5 years. it was reliable, but made the car a pain in the ass to work on. when they are running right under boost they make a god aweful amount of egt and underhood heat. they will melt anything that comes near them.

had a vortech s strim on an stock shortblock 91 lx before that. not as hard to work on, good power (540 rwhp with a small pulley), but to make them run hard you have to run a small pulley and a lot of belt tension. that will take its toll on the front main bearing with a cast crank. its not easy on the block either.

a friend of mine right now has a very simple little windsor. its a latemodel block, a scat 9000 408 kit, a set of TFS 190 TW heads, an OOTB victor jr, a pos carb, a c4 with 3.73s, small cam (236/242 under .600 lift), 10:1 compression, 1.75" mid length headers and off the foot brake it runs 10.80s@126 mph on the motor. and it only makes a hair over 400rwhp. unless you plan on spending a lot of $, keep it simple and build a big windsor with a cheap stock block and itll run.

I found some really good information on what is involved on a 351 swap. I have another question, could I reuse the wiring harness that is already in my mustang and swap out the ECUs or, do I have to run another wiring harness that comes with the ECU? Also, what about the headers and the exhaust, will I need to change those over? If I am going to do a engine swap, I rather spend all my money on that.

You won't need a new harness or ecu. They can both be used on the 351.

I have heard there are a few 5.0 longtube headers that work on the 351 and some don't. But there are also a few special headers designed for a 351 swap into a fox.

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Awesome! This makes me super happy to hear. You guys said it would be impossible to reach 500hp with a 302 block, right? What about the 351 EFI? How hard would it be to reach 500hp? Also, I mention I might stick in a turbo later on down the road, I am unsure if I still want to do that. I like the idea of having an all motor, just has a nice ring to it.